The main function of a smear staining machine is for making a blood smear and staining the blood smear if a microscopic examination is needed when abnormal events are found after a routine examination. In the process of making a test sample into a blood smear for the microscopic examination, a blood film should be processed for forming a proper appearance with suitable thickness according to characteristics of the sample to configure smearing parameters such as blood drop, smearing speed or smearing angle.
At present, conventional smear technology adjusts smearing parameters mainly based on the HCT value of the sample. The HCT value is defined as the percentage of red blood cells in a certain volume of whole blood, also termed the “hematocrit.” The hematocrit reflects characteristics of the blood sample in a certain perspective. It may look convenient, but some disadvantages appear as well at the same time, which are described below. Firstly, characteristics of the blood sample are not decided by the HCT value only. When the HCT value gets lower, the influence weight of the HCT value from characteristics of the sampling blood is more and more limited correspondingly.
On the other hand, blood plasma and internal suspended matter gradually become the main influence factors for characteristics of the blood sample. All kinds of environmental factors, such as environment temperature and humidity, storage period and preservation condition, influence the configuration of the blood film. For instance, by applying the same blood sample at the same smearing parameters, the blood film gets shorter and thicker when the environment temperature gets lower. On the contrary, the blood film gets longer and thinner when the environment temperature gets higher. In addition, the smear staining machine is designed to process abnormal samples, which usually come with a high percentage of low HCT value. Therefore, under the above conditions, the guiding function of the HCT value for the smear parameters would be reduced accordingly. Improper smear parameters may be acquired if smear parameters are adjusted in accordance with the HCT value so as to influence the effect of the blood film process.